PROJECT SUMMARY More than 60 employers and insurers now offer the Centers for Disease Control and Prevention (CDC) National Diabetes Prevention Program (DPP) as an evidence-based weight management program for employees. Health Plus, the workplace wellness division of Vanderbilt Health and Wellness, began offering the DPP in 2014 as a benefit to the approximately 25,000 employees of Vanderbilt University (VU) and Vanderbilt University Medical Center (VUMC). The goal of the DPP is for participants to lose 5% of their baseline weight by the end of the year-long program. From 2014-2017, the proportion of Health Plus DPP (HP-DPP) participants achieving this goal exceeded National DPP metrics (43.6% of HP-DPP participants versus 35.5% of DPP participants nationwide) and the program earned full recognition status from the CDC Diabetes Prevention Recognition Program. Yet comparisons of potential and actual participation in the HP-DPP suggest many employees likely to benefit from this highly effective program are not participating in it. Program reach is often limited for both worksite wellness programs and DPPs because of inconvenient locations, time limitations, insufficient incentives, and confidentiality concerns. Feedback collected from HP-DPP participants from 2014-2017 suggests the need to meet in person on the VU/VUMC main campus to participate in the program was a key barrier to its reach during this interval. However, the group structure of the program was noted to be a key source of support and motivation. To improve the reach of the highly effective HP-DPP while maintaining the benefits of its group structure, the HP-DPP introduced a video-teleconference (VTC) group (telehealth) participation option in 2018. Although the CDC endorses the use of telehealth as a DPP implementation strategy, few studies have compared the effectiveness of telehealth and in-person delivery platforms for achieving weight loss. No studies have compared weight loss outcomes for VTC and in-person DPP groups in which the VTC group participates solely via online interactions. The Centers for Medicare and Medicaid Services (CMS) recently decided not to reimburse DPPs utilizing a telehealth platform for program delivery without further testing and evaluation of virtual DPPs. Thus, the need for research to guide the use of telehealth as a DPP implementation strategy is relevant at both a local and national level. This project will evaluate the HP-DPP in terms of the reach, effectiveness, and implementation dimensions of the RE-AIM model by (1) comparing the reach, effectiveness, and implementation of the HP-DPP before versus after the introduction of the VTC participation option, (2) comparing the effectiveness and implementation of VTC versus in-person HP-DPP groups in the ?after? period, and (3) exploring reasons for differences in the reach, effectiveness, and/or implementation of the HP-DPP that are associated with inclusion of the VTC participation option using in-depth interviews. The results of this evaluation will directly inform efforts to extend the reach and public health impact of DPPs both within and beyond worksites.